Was driving on 91 north 1/2 mile or so from exit 17A/B and something caught my eye in the sky. I looked up and saw a rectangular object with rounded ends; it was about the color of gun metal grey, leaning towards a brown color. It did not appear to move sideways to me, but might have been coming towards me. Approximately two seconds later the object "dipped" and the sun appeared to reflect off the object, turning the object bright white. The object looked different as it moved/dipped, going from a rectangular object to something trapezoidal. Almost immediately after this it disappeared, as if it "blinked" or was "switched" off.